Synthesis and Characterization of Photosensitizers

Synthesis, isolation and analysis of HPPH and its 17² methylester derivative HPPH-ME [19 (link)], PS-531-COOH and PS-531-ME [19 (link)], erlotinib-conjugates PS-908 [10 (link)], and PS 5 to PS 43 (Figure 1) [11 (link)] have been previously reported. Each PS preparation used for tissue culture and in vivo studies has been verified by mass spectrometry and nuclear magnetic resonance analysis for purity of >96% and to be without trace of free erlotinib. Stock solutions of the PSs with concentrations ranging from 0.3 to 1.2 mM were prepared in H₂O containing 5% glucose, 0.1% Tween 80 and 0.1% ethanol and diluted in culture medium or injection solution immediately prior to use. The concentrations of PSs in the treatment media were confirmed by using medium aliquots, diluted 10-fold in methanol, removed precipitated proteins by centrifugation and determined PS concentration in the supernatant by fluorometry. Stock solution of erlotinib (Cell Signaling Technology, Danvers, MA, USA) was prepared in DMSO (10 mM) and aliquots diluted into medium for cell treatment.